Spatial separation of photo-generated electron-hole pairs in BiOBr/BiOI bilayer to facilitate water splitting.
Spatial separation of photo-generated electron-hole pairs in BiOBr/BiOI bilayer to facilitate water splitting.
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BiOBr/BiOI 双层中光生电子空穴对的空间分离以促进水分解
DOI：
10.1038/srep32764
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发表时间：
2016-09-02
影响因子：
4.6
通讯作者：
Lau WM
中科院分区：
文献类型：
--
作者：
Tang ZK;Yin WJ;Le Zhang;Wen B;Zhang DY;Liu LM;Lau WM
用密度泛函理论研究了BiOX1/BiOX2双层膜(X1和X2分别为氯、溴、碘)的电子结构和光催化性能。简单地说，它们的禁带宽度在1.85~3.41 eV之间，适合于太阳光的吸收，并且所有的双层膜都有有利于光催化裂解水的带线。其中，非均质BiOBR/BiOI双层膜的禁带宽度最小，是最好的。更重要的是，BiOBR/BiOI的光激发导致电子供应到导带的最小值，局域态主要是BiOBr的铋，在那里可以持续H+/H_2半裂水反应。同时，这种光激发产生的空穴主要来源于BiOI在价带最大处的碘态，从而促进了水在BiOI上分解的O2/H2O半反应。详细的能带结构分析还表明，这种有趣的光生电子-空穴对的空间分离和水分裂的两个半反应有利于从2-5 eV获得较宽的光激发光谱；因此，BiOBr/BiOI双层膜可以作为一种有效的光催化剂来分解水，特别是在进一步优化其光吸收系数的情况下。
The electronic structures and photocatalytic properties of bismuth oxyhalide bilayers (BiOX1/BiOX2, X1 and X2 are Cl, Br, I) are studied by density functional theory. Briefly, their compositionally tunable bandgaps range from 1.85 to 3.41 eV, suitable for sun-light absorption, and all bilayers have band-alignments good for photocatalytic water-splitting. Among them, heterogeneous BiOBr/BiOI bilayer is the best as it has the smallest bandgap. More importantly, photo-excitation of BiOBr/BiOI leads to electron supply to the conduction band minimum with localized states belonging mainly to bismuth of BiOBr where the H+/H2half-reaction of water-splitting can be sustained. Meanwhile, holes generated by such photo-excitation are mainly derived from the iodine states of BiOI in the valence band maximum; thus, the O2/H2O half-reaction of water splitting is facilitated on BiOI. Detailed band-structure analysis also indicates that this intriguing spatial separation of photo-generated electron-hole pairs and the two half-reactions of water splitting are good for a wide photo-excitation spectrum from 2–5 eV; as such, BiOBr/BiOI bilayer can be an efficient photocatalyst for water-splitting, particularly with further optimization of its optical absorptivity.